Fuel Pressure: Testing and Inspection

Diagnostic Lead:

A1 STATIC FUEL PRESSURE
- Key "OFF", install fuel pressure gauge.
- Install test lead to Fuel Pump (FP) lead of Self-Test connector.
- Turn key "ON". Ground test lead to run fuel pump.
- Check pressure and compare to specification. Specifications
- If pressure is within specification, go on to test A3.
- If pressure is not with specification, continue with test A2.

A2 HYDRAULIC AND ELECTRICAL CIRCUIT CHECK
- Check the following possible causes:
- Plugged fuel filter (relpace filter and check again for proper pressure)?
- Check for system leaks.
- Check for kinked/restricted fuel lines.
- Low voltage to fuel pump (should be within 0.5 volts of battery voltage at pump connection)?
- Disconnect return fuel line and note if fuel is returning. If fuel is being returned, replace pressure regulator and check again for proper pressure.
- Inertia switch open? (Reset switch as required.)
- Wiring at fuel pump/tank connector loose or open?
- Fuel pump ground connection at chassis loose or damaged?
- Improper fuel pump relay operation (should operate when FP (test) lead is grounded with ignition switch in "RUN" position).
- Electronic Engine Controls (EEC) relay not operation.
- If service was required and made, repeat test A1.
- If no service was required, replace fuel pump and replace A1.

A3 CHECK VALVE TEST
- Remove ground from test lead and note pressure on gauge.
- Pressure should remain within 0.14 kPa (2 psi) for 3 minutes after lead is ungrounded.
- If pressure drops more than 0.14 kPa (2 psi), go on to test A5.
- If pressure remains within specification, continue with test A4.

A4 CIRCUIT LEAK CHECK
- Check fuel lines and connectors for leakage.
- Disconnect fuel return line and plug engine side.
- Momentarily activate fuel pump by grounding test lead.
- Allow pressure to rise to operating pressure.
- If pressure holds, replace pressure regulator and repeat A3.
- If pressure fails to increase to specification, replace fuel pump and repeat test A1.

NOTE: There may also be a leaking injector.

A5 ENGINE ON TEST
- Disconnect and plug the vacuum line connected to the pressure regulator.
- Start engine and run at idle. Fuel pressure should be as indicated in Specifications (Ignition On, Engine Off). Specifications
- If pressure is within specifications, go to to test A7.
- If pressure is not within specifications, continue with test A6.

A6 IDLE ENGINE SERVICE
- Check for the following:
- Restricted fuel filter.
- Restricted Fuel Line.
- Improper voltage to fuel pump.
- If service was required and performed, repeat test A1.
- If no service was required, replace fuel pump and repeat test A1.

A7 HIGH SPEED TEST
- With engine running at idle and vacuum line disconnected from pressure regulator, note fuel pressure.
- Rapidly accelerate engine and watch fuel pressure. Fuel pressure should remain within 0.35 kPa (5 psi) of starting pressure.

NOTE: Road test vehicle while monitoring pressure may be a better test under load conditions.